The present invention relates to implantable medical devices for delivering a liquid therapeutic substance to a delivery site within a patient. More particularly, it relates to systems and methods for sensing insertion of a needle into a septum port assembly provided with an implantable therapeutic substance delivery device.
A variety of implantable medical devices are available for treating patients. For example, an implantable therapeutic substance delivery devices are typically used to deliver infusion media or therapeutic substances (such as medication) to a patient at a regulated dosage. The implantable therapeutic substance delivery device (sometimes referred to as a drug pump or medicament pump) is implanted by a clinician into a patient at a location appropriate for the therapy. Typically, an infusion catheter is connected to an outlet of the device, and is implanted/positioned to infuse the therapeutic substance at the desired therapy site so as to treat a condition such as pain, spasticity, cancer, neurodegenerative diseases, trauma, diabetes, or other medical conditions. The term “implantable therapeutic substance delivery device” as used herein refers to any implantable device for delivering medicaments including, but not limited to, bladder pumps, accumulator pumps, fixed-rate bellows pumps, and the like, as well as implantable devices that do not necessarily include a pump.
In general terms, the implantable therapeutic substance delivery device commonly includes a drug reservoir containing a volume of the infusion media, along with a pump and/or metering mechanism to propel the infusion media in some metered or constant flow dosage to the desired location from the reservoir via the catheter. Over time, the therapeutic substance in the reservoir becomes depleted and it is necessary to refill the device with a new supply of therapeutic substance. In order to avoid the need for surgery to access and refill the device, it is desirable to have the ability to percutaneously refill the drug reservoir. This is commonly done by providing the delivery device with a fill port assembly that establishes fluid access to the drug reservoir from an exterior of the device. In this regard, a resilient, resealable septum is provided with the fill port assembly, and is accessible by percutaneously inserting a hypodermic needle through the skin and then the septum. Once the septum has been pierced, the hypodermic needle is fluidly connected to the drug reservoir such that the reservoir can be refilled. Additional septum-type ports can also be provided, such as a catheter access port.
Because the device is implanted within the patient and cannot be seen directly, care must be taken to ensure that the needle is properly placed into the fill port assembly before transferring liquids. If the needle is not located within the fill port assembly (e.g., is mistakenly inserted into the catheter access port, the needle does not pierce the septum, etc.), delivery of the infusion media through the needle can result in immediate delivery of a significant quantity of the drug to the patient, with potentially dire consequences. In addition, unintended failure to properly refill the drug reservoir may lead to significant complications for the patient when the needed medication is not dispensed at a later time.
In light of the above, efforts have been made to identify to the clinician a location of the fill port assembly relative to the patient's skin prior to insertion of the needle. For example, templates are well known, and can provide a general indication or map of the fill port location following palpating the device's periphery through the patient's skin. Additionally, electronic and/or magnetic systems have been suggested that provide the clinician with additional information generally indicative of the fill port assembly position. Regardless of how the clinician arrives at an initial estimation of fill port assembly location, upon inserting the needle through the patient's skin, the clinician normally must make a manual/tactile determination as to whether the needle tip has been correctly directed to the fill port assembly and has subsequently pierced through the septum. Most clinician's are relatively comfortable in making this determination as, based on experience, the clinician can tactilely sense or feel when the needle has been inserted through the septum. However, it is sometimes difficult to know with certainty whether the septum has been accessed, especially with thick-skinned patients. Further, as implantable therapeutic substance devices become increasingly reduced in size, the attendant tactile feedback will diminish.
In light of the above, a need exists for a needle-in-septum sensor for an implantable therapeutic substance delivery device, along with an indicator device for providing the clinician with a confirmation of desired needle positioning relative to the fill port.